[en] Short communication

[en] Unlike a conventional chemical industry, in a reprocessing plant, it is necessary to incorporate at the design stage provisions of decontamination remotely and decommissioning of the plant and demonstrate that it is possible to carry out the same safely. These provisions can also be used for good house-keeping of processing areas, there by preventing buildup of radioactivity in these areas. This will help in extending the life of the plant without major decommissioning of the plant. It has also been demonstrated in Plutonium Plant Trombay that decommissioning and reconstruction can be carried out without over exposure of any personnel. 4 refs., 1 tab., 2 figs

[en] SIM LOOP is a test rig for simulation studies necessary for optimisation of process parameters for online decontamination of reactor system piping and equipment of power reactors. This paper highlights the engineering features of SIM LOOP and discusses the design basis in brief. 2 figs., 1 tab

[en] The kinetics of the dissolution of magnetite (Fe₃O₄) by ascorbic acid alone and ascorbic acid in presence of different chelating agents have been studied at different acid concentrations and chelating agent concentrations and as a function of pH. The overall rate of reaction is dependent on the instantaneous surface area of the magnetite particles and the probable reaction mechanism involves electron transfer from ascorbate anion to protonated and or chelated ∼Fe^III sites on the surface of the magnetite particles. (author). 7 refs., 5 figs

[en] Extensive work carried out in optimisation of dilute chemical decontamination (DCD) process for Indian PHWR's has helped to understand the chemistry aspects of the dilute chemical decontamination process. Based on the laboratory investigations and the experiences gathered in the application of DCD process for the PHT systems of PHWRs, suitable modifications can be made to improve the efficacy of the process. 11 refs., 6 figs

[en] Decontamination and decommissioning features which are significantly different for non-reactor facilities as compared to nuclear reactors can be summarised as: potentially high levels of chemical toxicity and radiotoxicity of the alpha emitting radioisotopes, need for criticality control throughout, higher potential for spread of contamination, prompt decontamination/ decommissioning preferred over mothballing or entombing alternatives, complex radiological mapping and characterization situations and complex radiological protection requirements for occupational workers. A brief review of the various aspects of decommissioning of various nuclear installations are given. 7 refs

[en] The corrosion product oxides formed over the structural materials are transported to the core and are activated by the neutrons generated by the fission process. These activated corrosion products are transported back to the out-of-core surfaces and deposited on the surfaces. Increase in the radiation field caused by these deposited radionuclides leads to exposure of personnels involved in the maintenance of power plant. Dilute chemical decontamination (DCD) processes can be employed to remove the corrosion product oxides along with the radioactive contaminants from the PHT system surfaces, thereby achieving reduction in the radiation field around the system. During the dissolution of oxides by decontaminant, corrosion of base metal also occurs. Suitable inhibitors can be added to the system along with the decontaminating chemicals to control the metal corrosion. This paper describes the role of inhibitors in DCD process and the results of laboratory investigations, carried out to evaluate the various inhibitors, are discussed. (author). 3 refs., 1 tab

[en] The chemical decontamination of unit-2 of Rajasthan Atomic Power Station (RAPS) was done using a chemical formulation of dilute solution of picolinic acid and reductant. This is the first attempt in India for full system decontamination and experience gained in this decontamination are useful in many ways for the future decontamination of Indian PHWRs. Details of the results are given. 4 refs., 6 tabs

[en] Simulated studies are required to optimise the process parameters in developing dilute chemical decontaminants (DCD's) suitable for the efficient dissolution of all oxide compositions found in water reactor circuits. At times such facility is needed to demonstrate engineering feasibility as well. The reagents are required to be benign to reactor materials and to give rise to easily handled solid waste forms. A loop of this kind was planned and is described. The entire loop is accommodated on four skid mounted portable rigs and these are transportable in nature. These rigs can be used for component decontamination and it can be up graded if it is required for sub system decontamination. (author). 2 figs

[en] Chemical decontamination of both operating facilities as well as those for decommissioning is a well developed technology and some of the processes have been commercialized. However, whether adopting a commercial process or carrying it out in-house, before application there is need to do a thorough feasibility study taking into consideration all site specific and unit specific factors and also a cost - benefit analysis. In general, it is most beneficial in the case of an operating facility to carry out the chemical decontamination during a major maintenance shutdown just before undertaking maintenance of equipment in areas having high radiation fields, since recontamination is bound to occur over a period of time after restarting operation of the facility. 1 tab